A prior art magnetic particle clutch, which has an axial cylindrical cavity, is described in the publication, entitled "Principles of Operation of Magneclutches and Magnebrakes," published by Sperry Flight Systems, dated November 1984, and is described hereafter.
A second prior magnetic particle clutch which has coils with slip ring conductors, and which has two radial cavities, is a modification of an existing design of the assignee, and is described hereafter.
The first prior art clutch includes an outer drive drum which has an axis and which has a radially inner surface, a coaxial inner driven drum which has a radially outer surface forming a cylindrical cavity with the radially inner surface and which is rotatable relative to the outer drive drum, magnetic particles disposed in the cylindrical cavity, and a coil unit for energizing the metal particles in the cavity.
The second prior art clutch includes an outer drive rotor which has an axis and which has a radially inner surface with an annular slot, a coaxial inner driven rotor which has an annular disk that is received in the annular slot forming a first annular radial cavity and a second annular radial cavity, magnetic particles disposed in the first radial cavity and the second radial cavity, a first set of coils and a second set of coils respectively energizing the magnetic particles in the first radial cavity and the second radial cavity, and a slip ring conductor which is mounted on the outer drive rotor and which is connected to the coils.
One problem with the first and second prior art clutches is that they are not suitable for use in a device which incorporates a change to the orientation of its axis of rotation during use, such as a helicopter, because the magnetic particles are shifted an excessive amount by the effects of centrifugal force and gravity force during the device start-up and flight.